Servo Motor / Actuator
The muscles of the burner. Servo motors provide precise positioning for air dampers and fuel valves, ensuring the optimal air-to-fuel ratio for efficient combustion.
Role in Combustion
Servo motors (or actuators) are electromechanical devices that convert control signals from the Burner Management System (BMS) into mechanical movement. They are critical for:
- Purging: Driving air dampers to full open position for pre-purge.
- Ignition: Moving to the ignition position for safe light-off.
- Modulation: Continuously adjusting air and fuel valves to match load demand while maintaining efficient combustion.
Control Methods
Floating (3-Point)
Uses two directional signals: one to open, one to close. If no signal is present, the motor holds its position.
Common in basic modulating burners.
Analog Modulating
Follows a proportional signal (e.g., 4-20mA or 0-10V). The motor position directly corresponds to the signal value.
Used for precise control loops.
Digital / Bus Communication
Connects via CanBus or Modbus to digital burner controllers (like Siemens LMV5). Provides extreme precision (0.1 degree accuracy) and real-time feedback on position, torque, and errors.
Key Specifications
| Torque | Typically 1.5Nm to 60Nm. Higher torque needed for large dampers. |
| Running Time | Time to rotate 90°. Ranges from 4s (fast) to 60s (slow/stable). |
| Shaft Type | Square, D-shaft, or keyed. Must match the linkage or valve coupling. |
| Feedback | Potentiometers (135Ω, 1000Ω) or auxiliary switches for position verification. |
Leading Manufacturers
- SiemensSQM, SQN series
- HoneywellModutrol, MT series
- BelimoHVAC & Industrial actuators
- Berger LahrSTA / STM series (Schneider)
- ArisIndustrial actuators
Related Components
Did you know?
In electronic fuel-air ratio control systems (like Siemens LMV), separate servo motors are used for air and fuel, allowing for "hysteresis-free" operation and much higher efficiency than mechanical linkages.